Permeability pore pressure

An important safety feature on every modern rig is the blowout preventer (BOP). As discussed earlier on, one of the purposes of the drilling mud is to provide a hydrostatic head of fluid to counterbalance the pore pressure of fluids in permeable formations. However, for a variety of reasons (see section 3.6 Drilling Problems ) the well may kick , i.e. formation fluids may enter the wellbore, upsetting the balance of the system, pushing mud out of the hole, and exposing the upper part of the hole and equipment to the higher pressures of the deep subsurface. If left uncontrolled, this can lead to a blowout, a situation where formation fluids flow to the surface in an uncontrolled manner. 

These should be con describe the same reaction, s but at the limit of fine Physically the interesting f appearance of the pressure p ablej with the consequence describe the system at the at the limit of fine pores, true that the pressure wit ni sense that percentage variat of the pressure variations i permeability, so convective permeability and pressure gr the origin of the two terms... 

Coimectivity is a term that describes the arrangement and number of pore coimections. For monosize pores, coimectivity is the average number of pores per junction. The term represents a macroscopic measure of the number of pores at a junction. Connectivity correlates with permeability, but caimot be used alone to predict permeability except in certain limiting cases. Difficulties in conceptual simplifications result from replacing the real porous medium with macroscopic parameters that are averages and that relate to some idealized model of the medium. Tortuosity and connectivity are different features of the pore structure and are useful to interpret macroscopic flow properties, such as permeability, capillary pressure and dispersion. 

Alixant, J-L., Real-time Effective Stress Evaluation in Shale Pore Pressure and Permeability Estimation, Ph.D. dissertation, Louisiana State University, p. 210, December 1989. 

The removal of PhCs by NF membranes occurs via a combination of three mechanisms adsorption, sieving and electrostatic repulsion. Removal efficiency can vary widely from compound to compound, as it is strictly correlated to (a) the physicochemical properties of the micro-pollutant in question, (b) the properties of the membrane itself (permeability, pore size, hydrophobicity and surface charge) and (c) the operating conditions, such as flux, transmembrane pressure, rejections/recovery and water feed quality. 

Shapiro, S., Patzig, R., Rothert, E. Rindschwentner, J. 2003. Triggering of seismicity by pore pressure perturbations permeability-related signatures of phenomenon. Pure and Applied Geophysics, 160, 1051-1066. 

It is unlikely, however, that the lithification of chalk will go on without consolidation, in which the volume of chalk material is reduced in response to a load on the chalk. Consolidation can lead to a reduction in porosity up to about 40%, and an increase in the effective stress (Jones et al., 1984). The increased effective stress is required to instigate the process of pressure solution. Pressure solution provides Ca2+ and HCO3 for early precipitation of calcite cement in the chalk. However, the inherently low permeability of chalk would inhibit the processes of consolidation and pressure solution/cementation unless some permeable pathways are opened up to permit the dissipation of excess pore pressure created by the filling of pore space by calcite cement. Pressure solution will cease if the permeable pathways are blocked by cement. Thus, it appears that the development of fractures, open stylolites and microstylolitic seams (Ekdale et al., 1988) is necessary to permit pressure solution to continue and lead to large rates of Ca2+ and HC03 mobilization. 

The delivery profile of the pump is controlled by the characteristics of the semi-permeable membrane (such as permeability, pore size, and thickness), the osmotic pressure difference across the membrane and the dimensions of the orifice. 

David C., Wong T., Zhu W., and Zhang J. (1994) Laboratory measurement of compaction-induced permeability change in porous rock implications for the generation and maintenance of pore pressure excess in the crust. Pure Appl. Geophys. 143, 425-456. 

Zhang C. F., Tullis T. J., and Scruggs V. J. (2001) Implications of permeability and its anisotropy in a mica gouge for pore pressures in fault zones. Tectonophysics 335, 37-50. 

Heat pipe thermal resistanee (and the heat transfer eoeffieient in the evaporator and eondenser zones) was found using the data of the vapour temperature in the adiabatie zone and the mean temperature in the evaporator and in the eondenser. The heat transfer eoeffieients in the evaporator and eondenser of the flat mHPs depend on two- dimensional hydraulie (pore saturation, eapillary permeability, eapillary pressure) and thermal (temperature distribution along the heat pipe envelope) parameters of deviee. The temperature in the middle of the heated side (heat load input) of the evaporator ean exeeed the symmetrie point temperature on the opposite (non-heated) surfaee of the envelope by nearly 10 °C. 

If the flux of pore water relative to the sediments can be determined, one can calculate the effective permeability of pressure seals for different potenti-ometric gradients, assuming Darcy flow (see Appendix A). 

Analysis of the RFT-data combined with detailed sequence stratigraphic studies were performed to obtain representative pore-pressure gradients from top to base of the individual permeable sands. Fig. 7 shows the interpreted pressure gradients for the Juras-sic-Triassic sequences within hydraulic compartment I based on RFT data from wells 10-1 and 10-2. Figs. 8 and 10 illustrate the same for hydraulic compartment II (based on wells 7-1, 7-2 and 7-4) and hydraulic compartment III (based on wells 7-3 and 7-5) respectively. 

A third constraint is related to the potential cross flow situation in the annulus across permeable formations. The main flow path is of course along the well bore axis. But because, during the operation, the pressure in the annulus is always higher than the pore pressure of the formation fluids, the annular fluids are likely to leak off into the formation pores. This phenomenon should be minimized as the objective is obviously not to loose these fluids into the formations. Another possible consequence is the damage that the lost fluid may cause to the permeability of hydrocarbon bearing formations thus making the production of formation fluids more difficult. 

The development and dissipation of excess pore water pressures in the vicinity of the advancing tunnel (at the time of the FEBEX tunnel excavation) was a clear example of hydromechanical interaction. It was concluded that the development of pore pressures was controlled by the initial stress field state, by the rate of excavation and by the permeability and drainage properties of the granite. However, the available information on the intensity and direction of principal stresses in the area was found inconsistent with the actual measurements. The problem posed by this discrepancy was essentially unsettled since a precise determination of the initial stress state in the vicinity of the FEBEX tunnel was not available. 

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